During the past two decades or so, personalized medicine has gotten a lot of hype. The promise is this: researchers can use a person’s genetic data to help guide disease treatment and, in some cases, extend that person’s life expectancy when they are sick. The concept seems to make a lot of sense—nobody wants impersonal or imprecise medicine, and advocates point to success stories such as chimeric antigen receptor (CAR) T cell therapy, a personalized immunotherapy that has proved useful against certain cancers. But as James Tabery argues in his new book, Tyranny of the Gene, genetically customized drug regimens are not as effective or widely applicable as they are made out to be.

Tabery, a professor of philosophy at University of Utah, who focuses on medical ethics, saw the promise of personalized medicine when his father was diagnosed with stage 4 non-small-cell lung cancer in August 2011. After a test revealed that the cancerous cells had a certain molecular marker, Tabery’s father was prescribed a treatment that could target the cells accordingly. The tumors shrank, and he lived for 13 months. It’s impossible to know “how much time the drugs added to the end of my father’s life, but there is every reason to believe he lived longer because of them,” Tabery says. Looking back at the experience a few years later, however, he is unconvinced that such efforts are the best route to better health.

Scientific American spoke to Tabery about his motivation for chronicling the rise of personalized medicine and the reasons he thinks paying attention to the environment might have a bigger impact on health care.

[An edited transcript of the interview follows.]

How would you describe the difference between personalized and precision medicine?

The vision of personalized medicine that was portrayed to the public from about 1997 to 2007 was that [researchers] took your genome and, in return, gave you a tailor-made drug. Precision medicine is just a personalized medicine [rebranding that was done] by the genetics community in 2011 because they were concerned that the language of “personalized” was confusing people. Now there are two confusing terms out there, neither of which are entirely accurate.

We’re told that precision medicine gets at causes, whereas traditional medicine does not, and that it gives us diagnostic clarity and accuracy in a way that traditional medicine did not. What’s misleading about that is it’s an illusion that all those problems [of uncertainty and differing treatment recommendations] go away.

What makes personalized, or precision, medicine seem so promising?

It sounds intuitively attractive. We like the warm, fuzzy feeling that each of us is unique and each of us is different. But it’s not like personalized medicine is astrology or snake oil. There are clear cases where people today are alive—taking medicines that are a result of this genomic revolution—whereas 10 to 20 years ago they would be dead. The classic example is people who have chronic myelogenous leukemia and take Gleevec [a treatment that extends life expectancy for people with this disease by at least five years].

I certainly don’t want to suggest that we should diminish the fact that those people are living longer. The concern on my part is that I think these [successes] are exceptions. When you move out of the space of rare diseases and cancers, it becomes increasingly difficult to see where [personalized medicine] gets the same kind of purchase.

The things that lead to most illness and death in society––forms of diabetes or cardiovascular disease, COPD [chronic obstructive pulmonary disease] or obesity––this personalized medicine stuff is not going to help them. [But people who have these conditions] are being lured by doctors and pharmaceutical companies into a view that it will. For instance, researchers are going into communities of color and saying, “Help us battle racial health disparities by giving us your DNA.” I find it really troubling because there’s all this evidence that suggests the causes of health disparities are not in our DNA; they’re in our environments. I worry that it’s both misleading and distracting from research that could actually be done to focus on the things that are causing the illness.

Much of your book chronicles how, in the past two and a half decades, the National Institutes of Health gravitated toward genetics research rather than research on environmental and social factors that affect health. Why is this history important?

A historical lens is always helpful for understanding how we got to the place we are today. The competition [between genetics research and environmental research] that played out at the National Institutes of Health since the late 1990s illustrates this other path that we could have taken, where we [could have gone] all in on asking: What are the environmental contributions to health and illness? For instance, I think we need to give more support to researchers who are doing social and behavioral research on how racism actually [affects health] and what sort of interventions can be done to combat racism in the workplace or in schools.

You focus a lot on the expense of precision medicine. How does it exacerbate inequality?

The way personalized medicine works is: you get information from patients about their genomics, and what follows is pharmacogenetics, which is, essentially, you get this drug based on how you metabolize drugs. In the circumstances where personalized medicine does work [on rare diseases and cancers], both the genetic tests and the drugs themselves are astronomically priced. For a small number of people [for whom] personalized medicine is relevant to their health condition, they’re going to be staring down the barrel of really expensive treatments [that likely would not be fully covered by insurance].

The drugs cost lots of money because they’re going to a smaller number of people, compared with the cost of giving the same drug to everyone. It tends to disadvantage people who are already marginalized because now they’ve got this additional economic barrier.

The example in my introductory chapter is the lung cancer case. We’ve long known that the best shot at combating lung cancer is catching it early and surgically removing it before it’s metastasized. Once it’s metastasized, the prognosis is really bad. But Black people were getting these surgeries less often than white people. And when you move to the era of personalized medicine, Black people are getting tested for whether or not a drug is a good fit for them less often than white people. People from poor neighborhoods are getting tested less often than people from wealthier neighborhoods.

I do give the genetics community credit because they are very tuned in to this problem. They are worried about it.

How do you think personalized medicine will evolve?

There’s no sign of it slowing down—it’s exploding. There’s this idea now that we should do whole-genome sequencing on every baby born in the U.S., the argument being that if we’re able to catch any rare diseases early, then maybe we could treat them earlier. Is that realistic?

As the price of doing genomic sequencing continues to drop, and the financial value of getting more and more data goes up, there’s this huge bipartisan support for genomics. Meanwhile you’ve got Republican presidential candidates calling for eliminating the Environmental Protection Agency. This sort of drives home for me how there’s all this momentum for [genetics research and personalized medicine], and there are all these headwinds for [researching environmental health factors]. As we become increasingly politically polarized, doing things on the environmental side––whether that’s intervention or research––is going to be tough.